From the mid-1960s until 2010 it was generally believed that “The King’s Malady” from which George III suffered in 1765, 1788–89, 1801, 1804 and 1810–20 was the rare blood disease porphyria. This was a consequence of a theory vigorously promoted by Dr Ida Macalpine and her son Dr Richard Hunter in their book in the late sixties. The theory gained lasting popular traction in large part from its repetition in Alan Bennett’s 1991 play The Madness of George III, and the subsequent movie adaptation in 1994, in both of which porphyria was presented as the concluding diagnosis of “The King’s Malady”.
It is now clear that the porphyria theory was wrong. It was based on a large number of misconceptions and a highly selective use of evidence; it contained factual errors, flawed reasoning and the ignoring or downplaying of evidence that contradicted the authors’ thesis. Macalpine and Hunter had no clinical experience in diagnosing or treating porphyria, and presented an intellectually disingenuous case that the illness was physiological rather than psychological. This was a thesis that broadly aligned with various other theories they had expressed regarding mental illness in general, but crucially it did not fit the facts of George III’s actual condition.